The sequence of the first five N-terminal amino acids was determined and was found to be Met-Ile-Pro-Thr-Glu.

Dimers and Aggregates

1% as determined by silver-stained SDS-PAGE gel analysis.

Biological Activity

rHuIL-5 is fully biologically active when compared to standard. The ED50 as determined by the dose-dependent stimulation of the proliferation of TF-1 cells was found to be less then 0.15ng/ml, corresponding to a Specific Activity of 6 x 10e6 IU/mg.

Endotoxin

0.1ng/ug (IEU/ug) of rHuIL-5.

Protein Content

Protein quantitation was carried out by two independent methods:

1. UV spectroscopy at 280 nm using the absorbency value of 0.625 as the extinction coefficient for a 0.1% (1mg/ml) solution. This value is calculated by the PC GENE computer analysis program of protein sequences (IntelliGenetics).

2. Analysis by RP-HPLC, using a standard solution of IL-5 as a Reference Standard.

Reconstitution

Reconstitute the lyophilized rHuIL-5 in sterile ddH2O not less than 100ug/ml, which can then be further diluted to other aqueous solutions.

Storage and Stability

Lyophilized powder may be stored at 4°C for short-term only. Reconstitute to nominal volume by adding sterile dH2O and store at -20°C. Reconstituted product is stable for 12 months at -20°C. For maximum recovery of product, centrifuge the original vial prior to removing the cap. Further dilutions can be made in assay buffer.